In a press conference this afternoon, President Obama said he was "deeply concerned" by reports of Russian troops mobilizing in Ukraine's Crimea region. Obama also emphasized that "there will be costs" for any military intervention in Ukraine.
"It would present a profound interference in matters that must be decided by the Ukrainian people," he said, adding, "it would invite the condemnation of the international community."
"The United States will stand with the international community in affirming that there will be costs for any military intervention in Ukraine."
This morning, troops in unmarked uniforms seized two airports in Crimea. Ukraine's acting interior minister, Arsen Avakov, said the armed men were Russian troops, but, according to the Daily Beast, the men are part of a private security group hired by the Russian military.
Reporters from the BBC also spotted Russian transport vehicles entering the region and witnesses reported seeing at least eight Russian military helicopters enter the region (unconfirmed video of which can be seen here). Reporters from the Global Post also filmed alleged Russian military convoys driving through Crimea.
Later in the day, a "Kiev official" told the AFP and Sky News that more than 2,000 Russian troops landed in Crimea as part of an "armed invasion." Ukraine's acting president, Oleksandr Turchynov, released a statement, condemning the reported military intervention from Russia.
"In an act of naked aggression against Ukraine, and under the pretense of military exercises, Russia has brought military forces into the Autonomous Republic of Crimea. Not only have they seized Crimea's parliament and Council, they've tried to take control of civilian facilities and communications, and tried to block the positions of Ukrainian forces.
"They are provoking us into an armed conflict. Based on our intelligence, they're working on scenarios analogous to Abkhazia, in which they provoke conflict, and then they start to annex territory.
"Ukraine's military will fulfill its duties, but will not succumb to provocation, and is not entering into armed conflict, understanding the high danger that this would expose to the civilian population of Crimea."